The present invention relates to a fuel injection device for pressurizing fuel within a fuel reservoir by a fuel pump and for injecting and feeding the pressurizing fuel to an engine through a fuel injection valve installed in a fuel distribution pipe, and more particularly to a fuel feed device in a motorcycle fuel injection device installed on a motorcycle.
In general, in a motorcycle, a fuel reservoir is disposed in an upper position and an engine is disposed in a lower position in a gravity direction, and a throttle body, a fuel distributor provided with a fuel injection valve, fuel pump, a fuel pressure control valve, a filter or the like are disposed in a space formed between the engine and the fuel reservoir. In view of the installability of the fuel feed device composed of the fuel pump, the fuel pressure control valve, the filter and the like to the motorcycle, the assembling property, and the compactness, the respective components of the fuel feed device are received and arranged within a single casing.
For example, the present applicant has Japanese Patent Application No. 352292/1997.
According to this publication, the interior of the single casing is divided into a fuel chamber and a return fuel chamber, the fuel chamber is connected to the fuel reservoir and an intake passage of a fuel pump disposed within the return fuel chamber is opened to the above-mentioned fuel chamber.
Then, a longitudinal axis of the casing provided with the fuel chamber and the return fuel chamber is arranged in the horizontal direction in the motorcycle.
The reason for the longitudinal axis of the casing being arranged in the horizontal direction as described above is that a plurality of throttle bodies each of which is connected to an associated intake pipe of a multi-cylinder engine are provided on the sides of the horizontal direction to thereby constitute a multiplicity of throttle bodies and the horizontal space formed along the multiplicity of throttle bodies may be utilized.
Then, the fuel within the fuel reservoir is caused to flow into the fuel chamber by the gravitational force and the fuel within the fuel chamber is sucked by the fuel pump. The fuel pressurized by the fuel pump is fed toward the fuel injection valve installed in the fuel distributor pipe.
The conventional fuel feed device for a motorcycle fuel injection device suffers from the following disadvantages.
(1) When the motorcycle travels in a normal way in a city area after traveling at a high speed for a long period of time, a smooth normal travel might be obstructed. This is because the engine temperature increases remarkably in the high speed travel and the elevated temperature increased an environmental temperature of the engine in the normal travel. PA1 (2) In a hot restart in which the engine is stopped after it has been operated continuously for a long period of time and the engine is started again in a short time, the quick start of the engine would be obstructed. This is because the forcible cooling for the engine has not been performed so that the engine temperature increases remarkably to thereby increase remarkably the environmental temperature of the engine. A remarkable increase in environmental temperature is due to the fact that the engine is started under such condition. PA1 a fuel flow chamber, a pump receiving chamber and a fuel discharge chamber are dividedly formed on a longitudinal axis X--X directing from one side to the other side, PA1 a fuel introduction passage is opened into said fuel introduction chamber; PA1 an intake passage of a fuel pump disposed within said pump receiving chamber is opened into said fuel introduction chamber and at the same time a discharge passage of said fuel pump is opened into said fuel discharge chamber; PA1 a fuel case in which a filter is disposed and a fuel discharge passage is opened into the filter and a fuel pressure control is provided in said fuel discharge chamber; PA1 a fuel pressure control valve to which the fuel introduction passage is opened and to which a fuel return passage opened and closed by a valve moved in synchronism with the diaphragm is provided in a fuel chamber which is divided from a spring chamber and the fuel chamber by the diaphragm; PA1 the longitudinal axis of said fuel case is arranged substantially in a vertical direction and said fuel introduction chamber is arranged below a bottom of a fuel reservoir; and PA1 said fuel introduction passage is in communication with said fuel reservoir and the fuel discharge passage is in communication with a fuel distributor pipe, the fuel introduction passage of said fuel pressure control valve is in communication with the fuel discharge chamber, wherein the fuel return passage is in communication with the fuel reservoir.
As described above, when the environmental temperature of the engine increases remarkably, the fuel temperature reserved in the fuel reservoir increases remarkably, resulting in the generation of a large amount of bubble in the fuel chamber. The bubble is caused to move upwardly by its own floating force and stagnant in the upper portion of the fuel chamber.
On the other hand, referring to the fuel pump, this fuel pump is disposed along the longitudinal axis of the casing so that the fuel pump is arranged in the horizontal direction. As a result, the flow direction of the fuel flowing through the fuel pump is in the horizontal direction.
According to the present invention, the bubble generated in the fuel chamber is not sucked in a small amount continuously to the fuel pump. There is a fear that the bubble would be sucked immediately after a constant amount or more of the bubble stagnant in the upper portion of the fuel chamber is stagnated. It is difficult to feed stably the fuel toward the fuel injection valve. It is also difficult to feed a sufficient and necessary amount of fuel to start the engine.